Six species of haplosclerid sponges are described from shallow waters in the coast of Rio de Janeiro state, southeastern Brazil (southwestern Atlantic). Three species: Amphimedon viridis Duchassaing & Michelotti, 1864, Callyspongia (Callyspongia) pallida Hechtel, 1965 and Oceanapia nodosa (George & Wilson, 1919) are already known from neighbouring biogeographic provinces (viz., the Caribbean) and the other three are new to science, viz., Callyspongia (Toxochalina) pseudotoxa sp. n., Arenosclera brasiliensis sp. n. (both provisional endemics from Rio de Janeiro state), and Haliclona melana sp. n. Ecological data, known pharmacological properties, and morphological variations along the geographic range of the species are discussed, and a key to the species described is given.